diff --git a/.changeset/pre.json b/.changeset/pre.json
index 50c743f31..559973ea8 100644
--- a/.changeset/pre.json
+++ b/.changeset/pre.json
@@ -25,6 +25,9 @@
     "@modelcontextprotocol/test-integration": "2.0.0-alpha.1"
   },
   "changesets": [
-    "beta-release"
+    "beta-release",
+    "cjs-support-v2-packages",
+    "codemod-iterations-5",
+    "post-dispatch-32021-http-400"
   ]
 }
diff --git a/packages/client/CHANGELOG.md b/packages/client/CHANGELOG.md
index b347fa782..98ca06c43 100644
--- a/packages/client/CHANGELOG.md
+++ b/packages/client/CHANGELOG.md
@@ -1,5 +1,16 @@
 # @modelcontextprotocol/client
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/client/package.json b/packages/client/package.json
index bade926d9..f96b681bc 100644
--- a/packages/client/package.json
+++ b/packages/client/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@modelcontextprotocol/client",
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Model Context Protocol implementation for TypeScript - Client package",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/codemod/CHANGELOG.md b/packages/codemod/CHANGELOG.md
index 2268799fd..88458c85a 100644
--- a/packages/codemod/CHANGELOG.md
+++ b/packages/codemod/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/codemod
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+
+- [#2412](https://github.com/modelcontextprotocol/typescript-sdk/pull/2412) [`ef120b2`](https://github.com/modelcontextprotocol/typescript-sdk/commit/ef120b2be0c3c3d80468c3d4a9f79be30bb0c0a3) Thanks [@felixweinberger](https://github.com/felixweinberger)! - v1-to-v2 migration fixes from continued real-world migrations (codemod iterations 5).
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/codemod/package.json b/packages/codemod/package.json
index 0552fff7b..803053fb2 100644
--- a/packages/codemod/package.json
+++ b/packages/codemod/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@modelcontextprotocol/codemod",
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Codemod to migrate MCP TypeScript SDK code from v1 to v2",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/core-internal/CHANGELOG.md b/packages/core-internal/CHANGELOG.md
index d05259451..cce2b6f28 100644
--- a/packages/core-internal/CHANGELOG.md
+++ b/packages/core-internal/CHANGELOG.md
@@ -1,5 +1,11 @@
 # @modelcontextprotocol/core-internal
 
+## 2.0.0-beta.1
+
+### Patch Changes
+
+- [#2399](https://github.com/modelcontextprotocol/typescript-sdk/pull/2399) [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Return HTTP 400 for a `MissingRequiredClientCapabilityError` (`-32021`) produced after dispatch. The spec mandates `400 Bad Request` for this error with no condition on where it arose, but only the pre-dispatch capability gate honored that; the post-handler emission — the `input_required` gate rejecting an embedded request whose required capability the caller did not declare — surfaced in-band on HTTP 200. The JSON-RPC error body is unchanged, every other error code (including a handler relaying a downstream peer's `-32020`/`-32022`) keeps the origin-keyed in-band behavior, and the mapping only applies while the response is uncommitted: an exchange that already streamed — or one hosted with `responseMode: 'sse'`, which opens its stream at dispatch end — keeps its committed 200 and carries the error in-stream.
+
 ## 2.0.0-alpha.3
 
 ### Major Changes
diff --git a/packages/core-internal/package.json b/packages/core-internal/package.json
index 0239af7cb..0514d3611 100644
--- a/packages/core-internal/package.json
+++ b/packages/core-internal/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@modelcontextprotocol/core-internal",
     "private": true,
-    "version": "2.0.0-beta.0",
+    "version": "2.0.0-beta.1",
     "description": "Model Context Protocol implementation for TypeScript - Core package",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/core/CHANGELOG.md b/packages/core/CHANGELOG.md
index 2345712ed..5d8653d16 100644
--- a/packages/core/CHANGELOG.md
+++ b/packages/core/CHANGELOG.md
@@ -1,5 +1,16 @@
 # @modelcontextprotocol/core
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/core/package.json b/packages/core/package.json
index 7a6f115e4..66e2802e2 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@modelcontextprotocol/core",
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Model Context Protocol for TypeScript — public Zod schemas (spec + OAuth/OpenID)",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/middleware/express/CHANGELOG.md b/packages/middleware/express/CHANGELOG.md
index 2cf344128..dd7b7f653 100644
--- a/packages/middleware/express/CHANGELOG.md
+++ b/packages/middleware/express/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/express
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+- Updated dependencies [[`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011), [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff)]:
+    - @modelcontextprotocol/server@2.0.0-beta.2
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/middleware/express/package.json b/packages/middleware/express/package.json
index 52c99d40a..f1c736a2b 100644
--- a/packages/middleware/express/package.json
+++ b/packages/middleware/express/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@modelcontextprotocol/express",
     "private": false,
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Express adapters for the Model Context Protocol TypeScript server SDK - Express middleware",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/middleware/fastify/CHANGELOG.md b/packages/middleware/fastify/CHANGELOG.md
index da75b01a6..71f574752 100644
--- a/packages/middleware/fastify/CHANGELOG.md
+++ b/packages/middleware/fastify/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/fastify
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+- Updated dependencies [[`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011), [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff)]:
+    - @modelcontextprotocol/server@2.0.0-beta.2
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/middleware/fastify/package.json b/packages/middleware/fastify/package.json
index 84b1c91ec..7f430b518 100644
--- a/packages/middleware/fastify/package.json
+++ b/packages/middleware/fastify/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@modelcontextprotocol/fastify",
     "private": false,
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Fastify adapters for the Model Context Protocol TypeScript server SDK - Fastify middleware",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/middleware/hono/CHANGELOG.md b/packages/middleware/hono/CHANGELOG.md
index 185c5a01b..d7e9f4828 100644
--- a/packages/middleware/hono/CHANGELOG.md
+++ b/packages/middleware/hono/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/hono
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+- Updated dependencies [[`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011), [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff)]:
+    - @modelcontextprotocol/server@2.0.0-beta.2
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/middleware/hono/package.json b/packages/middleware/hono/package.json
index e53942f33..3c280c0ec 100644
--- a/packages/middleware/hono/package.json
+++ b/packages/middleware/hono/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@modelcontextprotocol/hono",
     "private": false,
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Hono adapters for the Model Context Protocol TypeScript server SDK - Hono middleware",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/middleware/node/CHANGELOG.md b/packages/middleware/node/CHANGELOG.md
index 1ef2b9aae..ff35d59b7 100644
--- a/packages/middleware/node/CHANGELOG.md
+++ b/packages/middleware/node/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/node
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+- Updated dependencies [[`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011), [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff)]:
+    - @modelcontextprotocol/server@2.0.0-beta.2
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/middleware/node/package.json b/packages/middleware/node/package.json
index e8b22a447..aad6227dd 100644
--- a/packages/middleware/node/package.json
+++ b/packages/middleware/node/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@modelcontextprotocol/node",
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Model Context Protocol implementation for TypeScript - Node.js middleware",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",
diff --git a/packages/server-legacy/CHANGELOG.md b/packages/server-legacy/CHANGELOG.md
index e466d9d1f..72c273c85 100644
--- a/packages/server-legacy/CHANGELOG.md
+++ b/packages/server-legacy/CHANGELOG.md
@@ -1,5 +1,16 @@
 # @modelcontextprotocol/server-legacy
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/server-legacy/package.json b/packages/server-legacy/package.json
index ef2e8cf60..f571a3af9 100644
--- a/packages/server-legacy/package.json
+++ b/packages/server-legacy/package.json
@@ -1,7 +1,7 @@
 {
     "name": "@modelcontextprotocol/server-legacy",
     "private": false,
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Frozen v1 SSE transport and OAuth Authorization Server helpers for the Model Context Protocol TypeScript SDK. Deprecated; use StreamableHTTP and a dedicated OAuth server in production.",
     "deprecated": "This package is a frozen copy of v1's SSE transport and OAuth Authorization Server helpers for migration purposes only. Use StreamableHTTP from @modelcontextprotocol/server and a dedicated OAuth server in production. Will not receive new features.",
     "license": "MIT",
diff --git a/packages/server/CHANGELOG.md b/packages/server/CHANGELOG.md
index 9d4f37b99..9467763c0 100644
--- a/packages/server/CHANGELOG.md
+++ b/packages/server/CHANGELOG.md
@@ -1,5 +1,18 @@
 # @modelcontextprotocol/server
 
+## 2.0.0-beta.2
+
+### Patch Changes
+
+- [#2405](https://github.com/modelcontextprotocol/typescript-sdk/pull/2405) [`f172626`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f172626a8e98b2ae2f0f690e4afb4dc74dbf6011) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Ship CommonJS builds alongside ESM. Each package now emits both `.mjs`/`.d.mts`
+  and `.cjs`/`.d.cts` (via tsdown `format: ['esm', 'cjs']`), and its `exports` map
+  adds a `require` condition so `require('@modelcontextprotocol/…')` works from
+  CommonJS consumers. Output extensions are normalized across all packages
+  (`@modelcontextprotocol/core` moves from `.js`/`.d.ts` to `.mjs`/`.d.mts`); the
+  public import paths are unchanged.
+
+- [#2399](https://github.com/modelcontextprotocol/typescript-sdk/pull/2399) [`3c7ddaf`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c7ddafa05d8f17fb52168bf4638f09251c3d0ff) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Return HTTP 400 for a `MissingRequiredClientCapabilityError` (`-32021`) produced after dispatch. The spec mandates `400 Bad Request` for this error with no condition on where it arose, but only the pre-dispatch capability gate honored that; the post-handler emission — the `input_required` gate rejecting an embedded request whose required capability the caller did not declare — surfaced in-band on HTTP 200. The JSON-RPC error body is unchanged, every other error code (including a handler relaying a downstream peer's `-32020`/`-32022`) keeps the origin-keyed in-band behavior, and the mapping only applies while the response is uncommitted: an exchange that already streamed — or one hosted with `responseMode: 'sse'`, which opens its stream at dispatch end — keeps its committed 200 and carries the error in-stream.
+
 ## 2.0.0-beta.1
 
 ### Patch Changes
diff --git a/packages/server/package.json b/packages/server/package.json
index 9a0750ca4..d77e533db 100644
--- a/packages/server/package.json
+++ b/packages/server/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@modelcontextprotocol/server",
-    "version": "2.0.0-beta.1",
+    "version": "2.0.0-beta.2",
     "description": "Model Context Protocol implementation for TypeScript - Server package",
     "license": "MIT",
     "author": "Anthropic, PBC (https://anthropic.com)",